1. Field of the Invention
The present invention relates to an apparatus and method for calculating immunity from a radiated electromagnetic field which make possible high speed simulation of an electric current flowing through an electronic apparatus due to a radio wave radiated from an antenna and to a storage medium storing programs used for the same.
One of the new requirements being imposed by society on electronic apparatuses is that they not be affected by radio waves of under a certain level radiated from other electronic apparatuses. Tough regulations on this have been established in the major countries of the world.
Under radio wave regulations, examinations are conducted to determine if electronic apparatuses are affected by radio waves radiated from antennas. This has made necessary the development of technology for simulation of the effect of radio waves radiated from antennas on electronic apparatuses.
2. Description of the Related Art
The electric current and magnetic current flowing through parts of an object can be theoretically found by solving Maxwell's electromagnetic equations under given boundary conditions.
As a method of solving this, there is the moment method. The moment method is one of the methods of solving integration equations derived from Maxwell's electromagnetic equations by segmenting an object into small elements and therefore is able to handle any three-dimensionally shaped object. As a reference on the moment method, there is “H. N. Wang, J. H. Richmond, and M. C. Gilreath: “Sinusoidal reaction formulation for radiation and scattering from conducting surface”, IEEE TRANSACTIONS ANTENNAS PROPAGATION, vol. AP-23, 1975”.
The electric current and magnetic current flowing through elements are found by segmenting the configuration of an apparatus to be simulated into meshes, selecting a frequency to be processed, finding the mutual impedance, mutual admittance, and mutual reaction among the mesh-like elements for the selected frequency by performing predetermined computations, substituting the found mutual impedance etc. and a wave source specified by the configuration information into simultaneous equations under the moment method, and solving those equations.
That is, when handling a metal object, the metal portion is segmented into meshes as the object of analysis, the mutual impedance Z (value at frequency being processed) among mesh-like metal elements is found, and the simultaneous equations of the moment method standing among the mutual impedance Zij, a wave source Vi of that frequency component, and an electric current Ii of that frequency component flowing through the meshed metal elements:[Zij][Ii]=[Vi]where, [] indicates a matrix are solved to find the electric current Ii flowing through the metal elements.
Note that the mutual impedance shows the relationship between the electric field induced by the electric current flowing through an element and the electric current flowing through another element. The mutual admittance becomes necessary when considering the existence of a dielectric and shows the relationship between a magnetic field induced by a magnetic current passing through one element and the magnetic current passing through another element. The mutual reaction becomes necessary when considering the existence of a dielectric and shows the relationship between the electric field (magnetic field) induced by an electric current (magnetic current) flowing through one element and the magnetic current (electric current) passing through another element. An electric current flows through metal, while an electric current and magnetic current flow on the surface of the dielectric.
Up until the present time, the fact is that no technology for simulation of the effect of a radio wave radiated from an antenna on an electronic apparatus had been developed.
It has however now become possible to simulate the effect of a radio wave radiated from an antenna on an electronic apparatus by using the moment method.
That is, the electronic apparatus to be simulated and the antenna radiating the radio wave are set as a single object for application of the moment method, this is segmented into elements, and the mutual impedance etc. among elements are found by predetermined computations. The mutual impedance etc. found and wave sources specified by the configuration information (wave source of electronic apparatus and wave source of antenna) are substituted into the simultaneous equations of the moment method and the equations are solved so as to find the electric current and magnetic current flowing through the electronic apparatus. Therefore, it has become possible to simulate the effect of a radio wave radiated from an antenna on an electronic apparatus.
In view of this, the present inventors disclosed in Japanese Patent Application No. 9-90412, corresponding to U.S. Ser. No. 08/803,166 and German Patent Application No. 9710787.0, the use of the moment method to simulate the effect of a radio wave radiated from an antenna on an electronic apparatus.
In this invention, note was taken of the fact that if the frequency of the carrier wave is fc and the frequency of the modulation wave is fm, when amplitude modulation is applied, the frequency of the radio wave radiated from an antenna can be broken down into three parts, that is, fc, (fc+fm), and (fc−fm) and the moment method is applied by setting the electronic apparatus to be simulated and the antenna radiating the radio wave as a single object for application of the moment method, where the moment method is applied to these above three wave sources. Thus is becomes possible to simulate the effect of the radio wave radiated from an antenna on the electronic apparatus.
It is true that it is possible to simulate the effects of a radio wave radiated from an antenna on an electronic apparatus according to the invention of Japanese Patent Application No. 9-90412.
According to Japanese Patent Application No. 9-90412, however, it is necessary to calculate the mutual impedance, mutual admittance, and mutual reaction and solve simultaneous equations under the moment method for the frequency fc, to calculate the mutual impedance, mutual admittance, and mutual reaction and solve simultaneous equations under the moment method for the frequency (fc+fa), and to calculate the mutual impedance, mutual admittance, and mutual reaction and solve simultaneous equations under the moment method for the frequency (fc+fm).
This calculation of the mutual impedance, mutual admittance, and mutual reaction, however, takes an extremely long time. Due to this, there is the problem that high speed simulation of the effect of a radio wave radiated from an antenna on an electronic apparatus is not possible using the invention of Japanese Patent Application No. 9-90412.
Note that in the invention of Japanese Patent Application No. 9-90412, the present inventors mainly disclosed technology for simulation of an electric current, magnetic current, and intensity of an electromagnetic field in the time domain using the method of high speed calculation of the mutual impedance, mutual admittance, and mutual reaction disclosed in Japanese Unexamined Patent Publication (Kokai) No. 9-196986 (Japanese Patent Application No. 7-298062).
Further, to simulate the effect of a radio wave radiated from an antenna on an electronic apparatus, it is necessary that the intensity of the electric field applied to the electronic apparatus satisfy local legal requirements.
Japanese Patent Application No. 9-90412 does not consider this point, however. When using the invention of Japanese Patent Application No. 9-90412 to simulate the effect of a radio wave radiated from an antenna on an electronic apparatus, it is necessary to change the positions of the antenna and electronic apparatus on a trial and error basis for the simulation. There will therefore be the problem that high speed simulation of the effect of a radio wave radiated from an antenna on an electronic apparatus will not be possible.